Physiology and role of PCSK9 in vascular disease: Potential impact of localized PCSK9 in vascular wall

PCSK9 affects vascular senescence through the SIRT1 pathway

Age is an independent risk factor for atherosclerotic cardiovascular disease that increases the susceptibility of older adults to vascular intimal thickening, endothelial dysfunction, and thrombosis. However, the mechanism underlying vascular injury is not fully understood. In the present study, the effect of proprotein convertase subtilin-type kexin 9 (PCSK9) inhibitors on the senescent state of human umbilical vein endothelial cells (HUVECs) and on senescent mice and lipopolysaccharides (LPS) were assessed. The senescent state of mice was delayed under PCSK9 inhibitor treatment, and the expression of P16, P21, and P53 proteins in senescent cells was increased because LPS induction stimulated PCSK9 activation. PCSK9 overexpression accelerated cell senescence, activated a large number of oxidative stress pathways, and increased the expression of senescence-related genes (including P16, P21, and P53). In addition, inhibition of the sirtuin 1 (SIRT)1 oxidative stress pathway can attenuate the aging-promoting effects of PCSK9, which are elevated as a result of LPS induction. The SIRT1 activator was more efficient than LPS alone in inducing the expression of senescence-related genes. Therefore, PCSK9 inhibitors can delay the aging of the vascular by reducing cellular SIRT1 levels. Therefore, it can be concluded that PCSK9 inhibition inhibits vascular senescence by reducing the expression of senescent proteins by regulating the SIRT1 pathway.

The pleiotropic effects of PCSK9 in cardiovascular diseases beyond cholesterol metabolism

Cardiovascular diseases (CVD) are the leading cause of morbidity and mortality globally, with elevated low-density lipoprotein cholesterol (LDL-C) levels being a major risk factor. Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a critical role in regulating LDL-C levels by promoting the degradation of hepatic low-density lipoprotein receptors (LDLR) responsible for clearing LDL-C from the circulation. PCSK9 inhibitors are novel lipid-modifying agents that have demonstrated remarkable efficacy in reducing plasma LDL-C levels and decreasing the incidence of CVD. However, the broader clinical impacts of PCSK9 functions beyond cholesterol metabolism, including both desired and undesired effects from therapeutic PCSK9 inhibition, underscore the urgent necessity to elucidate the underlying mechanisms. Recent studies have shown that local PCSK9 in the vascular system can interact with other receptors such as CD36, LRP-1, and ABCA1. This provides new evidence supporting the potential contribution of PCSK9 to CVD through LDLR-independent signaling pathways. Therefore, this review aimed to outline the diverse effects of PCSK9 on CVD and discuss the underlying mechanisms in non-cholesterol-related processes, which will provide a rational basis for its long-term pharmacological inhibition in the clinic.

PCSK9-antibodies fail to block PCSK9-induced inflammation in macrophages and cannot recapitulate protective effects of PCSK9-deficiency in experimental myocardial infarction

Background and aims

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a crucial role in cholesterol homeostasis by regulating low-density lipoprotein (LDL) receptor levels. Despite its known effects on cholesterol metabolism, the role of PCSK9 in cardiac function, especially post-myocardial infarction (MI), remains unclear. This study investigates the impact of PCSK9 on heart function post-MI and evaluates the effects of PCSK9 inhibition via Alirocumab.

Methods

We used PCSK9 knockout (KO) mice and wildtype (WT) mice and in vivo treatment with Alirocumab to analyze cardiac function and survival post-MI induced by permanent ligation of the left anterior descending artery. PCSK9 and LDL receptor levels were measured using ELISA and qRT-PCR. Cardiac function was assessed via echocardiography and isolated working heart model experiments. Gene expression changes were evaluated using RNA sequencing, and inflammatory responses in bone marrow-derived macrophages (BMDMs) were analyzed in vitro.

Results

PCSK9 was expressed in murine heart tissue at levels comparable to the liver, despite minimal heart RNA expression. PCSK9 KO mice had lower plasma cholesterol levels and showed reduced cardiac functions in the working heart model compared to WT mice. Post-MI, PCSK9 KO mice demonstrated significantly improved survival and reduced ventricular rupture compared to WT mice. Alirocumab treatment, while effective in lowering plasma cholesterol, did not replicate the survival benefits seen in PCSK9 KO mice and even worsened cardiac function post-MI. In vitro, PCSK9 induced significant inflammatory responses in macrophages, which were not mitigated by Alirocumab.

Conclusion

PCSK9 accumulation in the heart post-MI contributes to adverse cardiac remodeling and inflammation. Genetic deletion of PCSK9 confers protection against post-infarct mortality, whereas pharmacological inhibition with Alirocumab fails to reproduce these benefits and may exacerbate cardiac dysfunction. These findings highlight the complex role of PCSK9 in cardiac pathology and caution against the assumption that PCSK9 inhibitors will necessarily yield cardiovascular benefits similar to genetic PCSK9 deficiency.

The Emerging Role of PCSK9 in the Pathogenesis of Alzheimer's Disease: A Possible Target for the Disease Treatment

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease mainly caused by β-amyloid (Aβ) accumulation in the brain. Among the several factors that may concur to AD development, elevated cholesterol levels and brain cholesterol dyshomeostasis have been recognized to play a relevant role. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protein primarily known to regulate plasma low-density lipoproteins (LDLs) rich in cholesterol and to be one of the main causes of familial hypercholesterolemia. In addition to that, PCSK9 is also recognized to carry out diverse important activities in the brain, including control of neuronal differentiation, apoptosis, and, importantly, LDL receptors functionality. Moreover, PCSK9 appeared to be directly involved in some of the principal processes responsible for AD development, such as inflammation, oxidative stress, and Aβ deposition. On these bases, PCSK9 management might represent a promising approach for AD treatment. The purpose of this review is to elucidate the role of PCSK9, whether or not cholesterol-related, in AD pathogenesis and to give an updated overview of the most innovative therapeutic strategies developed so far to counteract the pleiotropic activities of both humoral and brain PCSK9, focusing in particular on their potentiality for AD management.

Proprotein convertase subtilisin/kexin type 9 as a drug target for abdominal aortic aneurysm

PURPOSE OF REVIEW

There are no current drug therapies to limit abdominal aortic aneurysm (AAA) growth. This review summarizes evidence suggesting that inhibiting proprotein convertase subtilisin/kexin type 9 (PCSK9) may be a drug target to limit AAA growth.

RECENT FINDINGS

Mendelian randomization studies suggest that raised LDL and non-HDL-cholesterol are causal in AAA formation. PCSK9 was reported to be upregulated in human AAA samples compared to aortic samples from organ donors. PCSK9 gain of function viral vectors promoted aortic expansion in C57BL/6 mice infused with angiotensin II. The effect of altering PCSK9 expression in the aortic perfusion elastase model was reported to be inconsistent. Mutations in the gene encoding PCSK9, which increase serum cholesterol, were associated with increased risk of human AAA. Patients with AAA also have a high risk of cardiovascular death, myocardial infarction and stroke. Recent research suggests that PCSK9 inhibition would substantially reduce the risk of these events.

SUMMARY

Past research suggests that drugs that inhibit PCSK9 have potential as a novel therapy for AAA to both limit aneurysm growth and reduce risk of cardiovascular events. A large multinational randomized controlled trial is needed to test if PCSK9 inhibition limits AAA growth and cardiovascular events.

PCSK9 inhibition protects mice from food allergy

The Proprotein Convertase Subtilisin Kexin of type 9 (PCSK9) has been identified in 2003 as the third gene involved in familial hypercholesterolemia. PCSK9 binds to the membrane low-density lipoprotein receptor (LDLR) and promotes its cellular internalization and lysosomal degradation. Beyond this canonical role, PCSK9 was recently described to be involved in several immune responses. However, to date, the contribution of PCSK9 in food allergy remains unknown. Here, we showed that Pcsk9 deficiency or pharmacological inhibition of circulating PCSK9 with a specific monoclonal antibody (m-Ab) protected mice against symptoms of gliadin-induced-food allergy, such as increased intestinal transit time and ear oedema. Furthermore, specific PCSK9 inhibition during the elicitation steps of allergic process was sufficient to ensure anti-allergic effects in mice. Interestingly, the protective effect of PCSK9 inhibition against food allergy symptoms was independent of the LDLR as PCSK9 inhibitors remained effective in Ldlr deficient mice. In vitro, we showed that recombinant gain of function PCSK9 (PCSK9 D374Y) increased the percentage of mature bone marrow derived dendritic cells (BMDCs), promoted naïve T cell proliferation and potentiated the gliadin induced basophils degranulation. Altogether, our data demonstrate that PCSK9 inhibition is protective against gliadin induced food allergy in a LDLR-independent manner.

The role of PCSK9 in heart failure and other cardiovascular diseases-mechanisms of action beyond its effect on LDL cholesterol

Proprotein convertase subtilisin/kexin type-9 (PCSK9) is a protein that regulates low-density lipoprotein (LDL) cholesterol metabolism by binding to the hepatic LDL receptor (LDLR), ultimately leading to its lysosomal degradation and an increase in LDL cholesterol (LDLc) levels. Treatment strategies have been developed based on blocking PCSK9 with specific antibodies (alirocumab, evolocumab) and on blocking its production with small regulatory RNA (siRNA) (inclisiran). Clinical trials evaluating these drugs have confirmed their high efficacy in reducing serum LDLc levels and improving the prognosis in patients with atherosclerotic cardiovascular diseases. Most studies have focused on the action of PCSK9 on LDLRs and the subsequent increase in LDLc concentrations. Increasing evidence suggests that the adverse cardiovascular effects of PCSK9, particularly its atherosclerotic effects on the vascular wall, may also result from mechanisms independent of its effects on lipid metabolism. PCSK9 induces the expression of pro-inflammatory cytokines contributing to inflammation within the vascular wall and promotes apoptosis, pyroptosis, and ferroptosis of cardiomyocytes and is thus involved in the development and progression of heart failure. The elimination of PCSK9 may, therefore, not only be a treatment for hypercholesterolaemia but also for atherosclerosis and other cardiovascular diseases. The mechanisms of action of PCSK9 in the cardiovascular system are not yet fully understood. This article reviews the current understanding of the mechanisms of PCSK9 action in the cardiovascular system and its contribution to cardiovascular diseases. Knowledge of these mechanisms may contribute to the wider use of PCSK9 inhibitors in the treatment of cardiovascular diseases.

Proprotein convertase subtilisin/kexin type 9 deficiency in extrahepatic tissues: emerging considerations

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is primarily secreted by hepatocytes. PCSK9 is critical in liver low-density lipoprotein receptors (LDLRs) metabolism. In addition to its hepatocellular presence, PCSK9 has also been detected in cardiac, cerebral, islet, renal, adipose, and other tissues. Once perceived primarily as a "harmful factor," PCSK9 has been a focal point for the targeted inhibition of both systemic circulation and localized tissues to treat diseases. However, PCSK9 also contributes to the maintenance of normal physiological functions in numerous extrahepatic tissues, encompassing both LDLR-dependent and -independent pathways. Consequently, PCSK9 deficiency may harm extrahepatic tissues in close association with several pathophysiological processes, such as lipid accumulation, mitochondrial impairment, insulin resistance, and abnormal neural differentiation. This review encapsulates the beneficial effects of PCSK9 on the physiological processes and potential disorders arising from PCSK9 deficiency in extrahepatic tissues. This review also provides a comprehensive analysis of the disparities between experimental and clinical research findings regarding the potential harm associated with PCSK9 deficiency. The aim is to improve the current understanding of the diverse effects of PCSK9 inhibition.

20( S )-Protopanaxatriol Improves Atherosclerosis by Inhibiting Low-Density Lipoprotein Receptor Degradation in ApoE KO Mice

ABSTRACT

Atherosclerosis (AS) is a chronic progressive disease caused by various factors and causes various cerebrovascular and cardiovascular diseases (CVDs). Reducing the plasma levels of low-density lipoprotein cholesterol is the primary goal in preventing and treating AS. Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a crucial role in regulating low-density lipoprotein cholesterol metabolism. Panax notoginseng has potent lipid-reducing effects and protects against CVDs, and its saponins induce vascular dilatation, inhibit thrombus formation, and are used in treating CVDs. However, the anti-AS effect of the secondary metabolite, 20( S )-protopanaxatriol (20( S )-PPT), remains unclear. In this study, the anti-AS effect and molecular mechanism of 20( S )-PPT were investigated in vivo and in vitro by Western blotting, real-time polymerase chain reaction, enzyme-linked immunosorbent assay, immunofluorescence staining, and other assays. The in vitro experiments revealed that 20( S )-PPT reduced the levels of PCSK9 in the supernatant of HepG2 cells, upregulated low-density lipoprotein receptor protein levels, promoted low-density lipoprotein uptake by HepG2 cells, and reduced PCSK9 mRNA transcription by upregulating the levels of forkhead box O3 protein and mRNA and decreasing the levels of HNF1α and SREBP2 protein and mRNA. The in vivo experiments revealed that 20( S )-PPT upregulated aortic α-smooth muscle actin expression, increased the stability of atherosclerotic plaques, and reduced aortic plaque formation induced by a high-cholesterol diet in ApoE -/- mice (high-cholesterol diet-fed group). Additionally, 20( S )-PPT reduced the aortic expression of CD68, reduced inflammation in the aortic root, and alleviated the hepatic lesions in the high-cholesterol diet-fed group. The study revealed that 20( S )-PPT inhibited low-density lipoprotein receptor degradation via PCSK9 to alleviate AS.

Targeting PCSK9 as a key player in lipid metabolism: exploiting the therapeutic and biosensing potential of aptamers

The degradation of low-density lipoprotein receptor (LDLR) is induced by proprotein convertase subtilisin/kexin type 9 (PCSK9), resulting in elevated plasma concentrations of LDL cholesterol. Therefore, inhibiting the interactions between PCSK9 and LDLR is a desirable therapeutic goal for managing hypercholesterolemia. Aptamers, which are RNA or single-stranded DNA sequences, can recognize their targets based on their secondary structure. Aptamers exhibit high selectivity and affinity for binding to target molecules. The systematic evolution of ligands by exponential enrichment (SELEX), a combination of biological approaches, is used to screen most aptamers in vitro. Due to their unique advantages, aptamers have garnered significant interest since their discovery and have found extensive applications in various fields. Aptamers have been increasingly utilized in the development of biosensors for sensitive detection of pathogens, analytes, toxins, drug residues, and malignant cells. Furthermore, similar to monoclonal antibodies, aptamers can serve as therapeutic tools. Unlike certain protein therapeutics, aptamers do not elicit antibody responses, and their modified sugars at the 2'-positions generally prevent toll-like receptor-mediated innate immune responses. The focus of this review is on aptamer-based targeting of PCSK9 and the application of aptamers both as biosensors and therapeutic agents.

Targeted Degradation of PCSK9 In Vivo by Autophagy-Tethering Compounds

Proprotein convertase subtilisin/kexin type-9 (PCSK9), a secreted protein that is synthesized and spontaneously cleaved in the endoplasmic reticulum, has become a hot lipid-lowering target chased by pharmaceutical companies in recent years. Autophagosome-tethering compounds (ATTECs) represent a new strategy to degrade targeted biomolecules. Here, we designed and synthesized PCSK9·ATTECs that are capable of lowering PCSK9 levels via autophagy in vivo, providing the first report of the degradation of a secreted protein by ATTECs. OY3, one of the PCSK9·ATTECs synthesized, shows greater potency to reduce plasma low-density lipoprotein cholesterol (LDL-C) levels and improve atherosclerosis symptoms than treatment with the same dose of simvastatin. OY3 also significantly reduces the high expression of PCSK9 caused by simvastatin administration in atherosclerosis model mice and subsequently increases the level of low-density lipoprotein receptor, promoting simvastatin to clear plasma LDL-C and alleviate atherosclerosis symptoms. Thus, we developed a new candidate compound to treat atherosclerosis that could also promote statin therapy.

Polymorphisms rs562556 and rs2479409 of the PCSK9 gene associated with obesity and cardiovascular disease

OBJECTIVE

The primary objective was to comprehensively assess the association between single nucleotide polymorphisms (rs562556 and rs2479409) in the PCSK9 gene with biochemical parameters - C-reactive protein (CRP), glucose (GLU), triglyceride (TAG), low-density lipoprotein cholesterol (LDL CHOL), non-high-density lipoprotein cholesterol (non HDL CHOL), high-density lipoprotein cholesterol (HDL CHOL), cholesterol (CHOL), and anthropometric parameters (visceral fat), overweight/obesity and cardiovascular risk.

METHODS

A total of 71 women aged 23-64 years were divided into three groups based on body mass index (BMI). BMI ≥ 25/≥ 30 kg/m2 was the criterion for assessment of overweight/obesity. Anthropometric, biochemical and genetic examinations were performed on the probands. Changes in markers in each group and their association with cardiovascular risk were monitored.

RESULTS

We can conclude that in our study population we observed differences between the BMI categories for biochemical markers (CRP, LDL CHOL, non HDL CHOL, HDL CHOL, LDL CHOL) and anthropometric marker (visceral fat). Atherogenic index of plasma (AIP), Castelli's Risk Index I (CRI-I) and atherogenic coefficient (AC) confirmed high cardiovascular risk for the obese women category (0.045); (< 0.013); (< 0.010). Genotype and allele frequencies for the PCSK9 gene in the overweight and obese groups showed higher allele frequencies of allele A for both polymorphisms of the gene.

CONCLUSIONS

PCSK9 gene expression is associated with biological processes such as lipid metabolism and inflammation. Cholesterol-lowering therapies are the gold standard for reducing the risk of cardiovascular mortality and morbidity. Administration of monoclonal antibodies (mAbs) against PCSK9 is a novel lipid-lowering therapeutic approach in adults to reduce the risk of cardiovascular disease.

A Case of Multiple Intracranial Major Artery Stenoses With Coexisting PCSK9 p.E32K and RNF213 p.R4810K Variants

Objectives

Familial hypercholesterolemia (FH), caused by PCSK9 p.E32K, is characterized by early-onset coronary artery disease. However, the relationship between PCSK9 p.E32K and cerebrovascular disease is unclear. One of our patients with the PCSK9 p.E32K had several intracranial artery stenoses (ICAS). The objective of this case series was to identify factors that may be associated with ICAS in the variant carriers.

Methods

A 75-year-old Japanese woman with FH carrying PCSK9 p.E32K was found to have 5 asymptomatic ICAS when brain magnetic resonance angiography (MRA) was performed. We retrospectively investigated additional patients with FH who underwent brain MRA at our institution to explore the unknown factors accelerating ICAS.

Results

We investigated an additional 5 patients with FH who underwent brain MRA. Of them, only one had mild ICAS. The RNF213 p.R4810K that is an established genetic risk for ICAS, particularly in East Asians, was identified only in the patient with 5 ICAS.

Discussion

PCSK9 and RNF213 play an important role in lipid metabolism and endothelial integrity. Therefore, together, these variants could be involved in the development of multiple ICAS. Our case series indicated that PCSK9 p.E32K carriers should undergo early brain screening to obtain appropriate stroke prevention measures in the asymptomatic stage.

Efficacy and safety of PCSK9 inhibitors in patients with diabetes: A systematic review and meta-analysis

AIMS

Individuals with diabetes have increased cardiovascular risk. Although PCSK9 inhibitors bring about a wide reduction in lipids, there is uncertainty about the effects for diabetic patients. We conducted a systematic review and meta-analysis to assess the efficacy and safety of PCSK9 inhibitors for diabetes.

DATA SYNTHESIS

We performed a meta-analysis comparing treatment with PCSK9 inhibitors versus controls up to July 2022. Primary efficacy endpoints were percentage changes in lipid profile parameters. We used random effects meta-analyses to combine data. Subgroups of diabetic patients (by diabetes type, baseline LDL-C, baseline HbA1c and follow-up time) were also compared. We included 12 RCTs comprising 14,702 patients. Mean reductions in LDL-C were 48.20% (95% CI: 35.23%, 61.17%) in patients with diabetes. Reductions observed with PCSK9 inhibitors were 45.23% (95% CI: 39.43%, 51.02%) for non-HDL-cholesterol, 30.39% (95% CI: 24.61%, 36.17%) for total cholesterol, 11.96% (95% CI: 6.73%, 17.19%) for triglycerides, 27.87% (95% CI: 22.500%, 33.17%) for lipoprotein(a), 42.43% (95% CI: 36.81%, 48.06%) for apolipoprotein B; increases in HDL-C of 5.97% (95% CI: 4.59%, 7.35%) were also observed. There was no significant difference in fasting plasma glucose (FPG) (WMD: 2.02 mg/mL; 95% CI: -1.83, 5.87) and HbA1c (WMD: 1.82%; 95% CI: -0.63, 4.27). Use of a PCSK9 inhibitor was not associated with increased risk of treatment-emergent adverse event (TEAE) (p = 0.542), serious adverse event (SAE) (p = 0.529) and discontinuations due to AEs (p = 0.897).

CONCLUSIONS

PCSK9 inhibitor therapy should be considered for all diabetic individuals at high risk of atherosclerotic cardiovascular disease.

REGISTRATION CODE IN PROSPERO

CRD42022339785.

Novel triterpenoids from Alisma plantago-aquatica with influence on LDL uptake in HepG2 cells by inhibiting PCSK9

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has been regarded as an effective and exciting target in the treatment of atherosclerotic cardiovascular disease since 2003. Only two monoclonal antibodies have been approved in the market which, however, were also criticized for their high cost to $9000 per dose and delivery route. Exploration of natural new effective and cheaper small molecule alternatives with effective PCSK9 inhibition is feasible and desired.

PURPOSE

The aim of the study was to explore natural small molecules with anti-hyperlipidemia activity through PCSK9 from Alisma plantago-aquatica.

METHOD

A targeted isolation of triterpenoids from A. plantago-aquatica by LC-Orbitrap-QDa was conducted. The isolates were evaluated for their DiI-LDL uptake promoting activity with fluorescence intensity assayed in High-content Imaging System and PCSK9 inhibitory activity by Human PCSK9 Kit or western blot. The LDL uptake and PCSK9 level of target component in different concentrations and their mRNA level were further verified by corresponding kit, qPCR and western blot.

RESULTS

Six novel triterpenoids, including three unusual nor-triterpenoids (1-3) and three protostane-type triterpenoids (4-6), along with thirty-four known ones, were isolated from A. plantago-aquatica. Compound 2 had the lowest number of carbon atoms than previous reported nor-PTs in this plant. The 17 triterpenoids showed relatively remarkable activities in promoting LDL uptake with relevant structure-activity relationships. And 6 triterpenoids may improve LDL uptake in HepG2 cells by inhibiting PCSK9, especially for alisol G (28) with PCSK9 inhibition reaching to 55.6%, which demonstrated to increase LDLR mRNA or protein, and simultaneously reduce PCSK9 mRNA or protein significantly.

CONCLUSION

The protostane triterpenoids may serve as a new source for PCSK9 inhibitors.

PCSK9 and Other Metabolic Targets to Counteract Ischemia/Reperfusion Injury in Acute Myocardial Infarction and Visceral Vascular Surgery

Ischemia/reperfusion (I/R) injury complicates both unpredictable events (myocardial infarction and stroke) as well as surgically-induced ones when transient clampage of major vessels is needed. Although the main cause of damage is attributed to mitochondrial dysfunction and oxidative stress, the use of antioxidant compounds for protection gave poor results when challenged in clinics. More recently, there is an assumption that, in humans, profound metabolic changes may prevail in driving I/R injury. In the present work, we narrowed the field of search to I/R injury in the heart/brain/kidney axis in acute myocardial infarction, major vascular surgery, and to the current practice of protection in both settings; then, to help the definition of novel strategies to be translated clinically, the most promising metabolic targets with their modulatory compounds—when available—and new preclinical strategies against I/R injury are described. The consideration arisen from the broad range of studies we have reviewed will help to define novel therapeutic approaches to ensure mitochondrial protection, when I/R events are predictable, and to cope with I/R injury, when it occurs unexpectedly.

Proprotein Convertase Subtilisin Kexin 9 (PCSK9) and nonHDL Particles Rise During Normal Pregnancy and Differ by BMI

BACKGROUND

Serum lipids, including total cholesterol (TC), triglycerides (TG), and low-density lipoprotein cholesterol (LDL-c), increase during pregnancy. Serum Proprotein Convertase Subtilisin Kexin 9 (PCSK9) is a vital regulator in lipoprotein metabolism. Circulating PCSK9 downregulates the LDL receptor on the surface of liver cells inhibiting clearance of LDL-c.

OBJECTIVE

To determine the influence of weeks of pregnancy and obesity on circulating levels of essential lipid lipoproteins and PCSK9 in women with normal, uncomplicated pregnancies and deliveries.

METHODS

We performed a comprehensive lipid and lipoprotein profile during each trimester of pregnancy in 70 mostly Caucasian women with uncomplicated normal pregnancies and deliveries. Based on their first trimester BMI, we placed them into one of three categories: (<25 kg/m² n=23, 25-30 kg/m² n=25, or >30 n=22) kg/m². Cholesterol, triglycerides, LDL cholesterol (LDL-c), non-HDL particles, and lipoprotein(a) were measured by spectrophotometry, ion mobility, and immunoturbidimetric assays. Elisa assay determined PCSK9 (active and total). Homeostatic Model Assessment (HOMA-IR) assessed insulin resistance in the second and third trimesters of pregnancy.

RESULTS

Total and active PCSK9, LDL-c, and nonHDL particle concentrations were higher than reported for non-pregnant normal values, increased after the first trimester of pregnancy, and were highest from mid-gestation to the last trimester of pregnancy in the overweight and the obese.

CONCLUSION

PCSK9 levels rise as normal pregnancy progresses. Levels are higher in persons who are obese, even after adjustment for insulin resistance. Defining normal PCSK9 levels during pregnancy must adjust for gestational age and BMI.

Proteomic Profiling of Cryoglobulinemia

Objective

We aimed to explore and identify candidate protein biomarkers of cryoglobulinemia (CGE) in disease control patients with negative cryoglobulin (DC) or healthy controls (HCs).

Methods

The tandem mass tag (TMT)-labeled serum quantitative proteomics approach was used to identify differentially expressed proteins between the CGE and DC groups. Ingenuity pathway analysis was used for functional annotation of differentially expressed proteins. Biomarker candidates were validated in another cohort using the parallel reaction monitoring (PRM) method. Apolipoprotein A1 (APOA1), apolipoprotein CIII (APOC3), adiponectin, and proprotein convertase subtilisin/kexin type-9 (PCSK9), which represent key proteins involved in the cholesterol metabolism pathway, were further verified in an increased number of samples by enzyme-linked immunosorbent assay (ELISA).

Results

A total of 1004 proteins were identified, of which 109 proteins were differentially expressed between the CGE and DC groups. These differentially expressed proteins were primarily involved in hepatic fibrosis/hepatic stellate cell activation and immune/inflammation-related pathways. In the disease and biofunction analysis, these proteins were mainly associated with the adhesion of blood cells, leukocyte migration, cholesterol transport, and transport of lipids. Twelve candidate biomarkers were validated by PRM-based proteomics, and proteins involved in the cholesterol metabolism pathway were further verified. APOA1, APOC3, adiponectin and PCSK9 concentrations were increased in CGE patients compared with healthy controls (P=0.0123, 0.1136, 0.5760, and 0.0019, respectively).

Conclusion

This report describes the first application of a TMT-PRM-ELISA workflow to identify and validate CGE-specific biomarkers in serum. APOA1 and PCSK9 have been confirmed to be increased in CGE patients, demonstrating that proteins involved in cholesterol metabolism are also implicated in the development of CGE. These findings contribute to pathogenesis research and biomarker discovery in CGE.

Therapeutic possibilities of rehabilitation of patients who have undergone COVID-19 with residual changes in the lungs: A review

The article presents data on the mechanisms of formation of preservation of residual changes in lung tissue lesions in patients with a new coronavirus infection COVID-19. The main risk factors leading to the formation of lung tissue damage, such as age, severity of the disease, being on a ventilator, smoking, chronic alcoholism, are considered. The main directions of the search for antifibrotic drugs are presented. The rationale for the use of the pharmaceutical drug Longidaze is given, based on experimental and clinical studies. The main problems faced by doctors during the ongoing COVID-19 pandemic are identified. The schemes of administration of the drug Longidaze in patients with pulmonary fibrosis after a new coronavirus infection are considered.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) levels in primary antiphospholipid syndrome. The multicenter ATHERO-APS study

BACKGROUND

The proprotein convertase subtilisin/kexin type 9 (PCSK9) is emerging as a novel cardiovascular risk factor. Levels of PCSK9 in thrombotic primary antiphospholipid syndrome (PAPS) have never been investigated.

METHODS

Cross sectional comparison of baseline characteristics of 91 PAPS patients enrolled in the multicenter prospective ATHERO-APS cohort study. PCSK9 levels were categorized into tertiles and the association with arterial and recurrent thrombosis were assessed by univariable and multivariable logistic regression analysis.

RESULTS

Median age was 51 years and 71.4% (n = 65) were women. Overall, 33% (n = 30) experienced an arterial event while 31% (n = 28) had recurrent thrombotic events. Median PCSK9 levels were 1243 (1100-1650) pg/ml. Patients in the third PCSK9 tertile (>1458 pg/ml) showed a higher prevalence of dyslipidemia, lupus anticoagulant positivity and a history of previous arterial and recurrent thrombosis than patients in the first and second tertile. PCSK9 levels were higher in arterial than venous thrombosis (1502 vs. 1180 pg/ml, p = 0.002), and in patients with recurrent vs isolated thrombosis (1680 vs. 1150 pg/m, p < 0.001). High plasma PCSK9 levels were associated with a 4-fold increase risk for arterial events and with a 10-fold increase risk for recurrent thrombosis after adjustment for confounding factors.

CONCLUSION

These preliminary data suggest that PCSK9 levels are increased in PAPS patients with arterial and recurrent thrombosis. Its role as a possible therapeutic target in PAPS needs further studies.

Pleiotropic Effects of PCSK9: Focus on Thrombosis and Haemostasis

The proprotein convertase subtilisin/keying 9 (PCSK9) is a serine protease that has gained importance in recent years as a drug target, mainly due to its effect on cholesterol metabolism in promoting the degradation of the low-density lipoprotein receptor (LDLR). However, this protease may also play an important role in lipid-independent reactions, including the process of thrombogenesis. Considering this, we reviewed the effects and implications of PCSK9 on platelet function and blood coagulation. PCSK9 knockout mice exhibited reduced platelet activity and developed less agonist-induced arterial thrombi compared to the respective control animals. This is in line with known research that elevated blood levels of PCSK9 are associated with an increased platelet reactivity and total number of circulating platelets in humans. Moreover, PCSK9 also has an effect on crucial factors of the coagulation cascade, such as increasing factor VIII plasma levels, since the degradation of this blood clotting factor is promoted by the LDLR. The aforementioned pleiotropic effects of the PCSK9 are important to take into account when evaluating the clinical benefit of PCSK9 inhibitors.

Bibliometric analysis of the inflammatory mechanism in aortic disease

BACKGROUND

In view of the key role of inflammation in the pathogenesis of aortic disease, we visually analyzed the research hotspots of inflammatory mechanism in aortic disease in this work through the method of bibliometrics from the Web of Science (WOS) Core database over the past three decades.

METHODS

A visual bibliometric network of research articles on inflammatory mechanisms in aortic disease was obtained from VOSviewer and Citespace based on the WOS Core Collection.

RESULTS

A total of 1278 documents from January 1990 to February 2021 were selected for analysis. The United States and China had the highest percentage of articles, comprising 34.01% and 24.92% of articles worldwide, respectively. Harvard University has published the most articles in this field, followed by the University of Michigan and Huazhong University of Science and Technology. The top 3 research hotspots were atherosclerosis, oxidative stress, and macrophages. The journal with the most articles in this area was Arteriosclerosis Thrombosis and Vascular Biology, followed by Atherosclerosis and PLOS One. The research trend on inflammatory mechanisms in the aortic system has 5 distinct directions: (1) atherosclerosis, NF-κB, expression, smooth muscle cell, and oxidative stress; (2) coronary artery disease, C-reactive protein, risk factors, endothelial dysfunction, and aortic stenosis; (3) abdominal aortic aneurysm, matrix metalloproteinases, macrophage, and pathogenesis; (4) cholesterol, metabolism, low-density lipoprotein, gene expression, and a therosclerotic lesions; and (5) calcific aortic valve disease, interstitial cells, calcification, and stenosis.

CONCLUSIONS

Inflammatory mechanism research has shown a tendency to rise gradually in the aortic field. Numerous studies have explored the role of inflammatory responses in aortic disease, which may increase the risk of endothelial dysfunction (aortic fibrosis and stiffness) and induce plaque formation. Among them, NFκB activation, nitric-oxide synthase expression, and oxidative stress are particularly essential.

PCSK9 Imperceptibly Affects Chemokine Receptor Expression In Vitro and In Vivo

Proprotein convertase subtilin/kexin type 9 (PCSK9) is a protease secreted mainly by hepatocytes and in lesser quantities by intestines, pancreas, and vascular cells. Over the years, this protease has gained importance in the field of cardiovascular biology due to its regulatory action on the low-density lipoprotein receptor (LDLR). However, recently, it has also been shown that PCSK9 acts independent of LDLR to cause vascular inflammation and increase the severity of several cardiovascular disorders. We hypothesized that PCSK9 affects the expression of chemokine receptors, major mediators of inflammation, to influence cardiovascular health. However, using overexpression of PCSK9 in murine models in vivo and PCSK9 stimulation of myeloid and vascular cells in vitro did not reveal influences of PCSK9 on the expression of certain chemokine receptors that are known to be involved in the development and progression of atherosclerosis and vascular inflammation. Hence, we conclude that the inflammatory effects of PCSK9 are not associated with the here investigated chemokine receptors and additional research is required to elucidate which mechanisms mediate PCSK9 effects independent of LDLR.

PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) Triggers Vascular Smooth Muscle Cell Senescence and Apoptosis: Implication of Its Direct Role in Degenerative Vascular Disease

OBJECTIVE

PCSK9 (proprotein convertase subtilisin/kexin type 9) plays a critical role in cholesterol metabolism via the PCSK9-LDLR (low-density lipoprotein receptor) axis in the liver; however, evidence indicates that PCSK9 directly contributes to the pathogenesis of various diseases through mechanisms independent of its LDL-cholesterol regulation. The objective of this study was to determine how PCSK9 directly acts on vascular smooth muscle cells (SMCs), contributing to degenerative vascular disease. Approach and Results: We first examined the effects of PCSK9 on cultured human aortic SMCs. Overexpression of PCSK9 downregulated the expression of ApoER2 (apolipoprotein E receptor 2), a known target of PCSK9. Treatment with soluble recombinant human ApoER2 or the DNA synthesis inhibitor, hydroxyurea, inhibited PCSK9-induced polyploidization and other cellular responses of human SMCs. Treatment with antibodies against ApoER2 resulted in similar effects to those observed with PCSK9 overexpression. Inducible, SMC-specific knockout of Pcsk9 accelerated neointima formation in mouse carotid arteries and reduced age-related arterial stiffness. PCSK9 was expressed in SMCs of human atherosclerotic lesions and abundant in the "shoulder" regions of vulnerable atherosclerotic plaques. PCSK9 was also expressed in SMCs of abdominal aortic aneurysm, which was inversely related to the expression of smooth muscle α-actin.

CONCLUSIONS

Our findings demonstrate that PCSK9 inhibits proliferation and induces polyploidization, senescence, and apoptosis, which may be relevant to various degenerative vascular diseases.

PCSK9 as a new player in cancer: New opportunity or red herring?

Initially described as a factor involved in liver regeneration and neuronal differentiation, proprotein convertase subtilisin/kexin type 9 (PCSK9) has become one of the key regulators of low-density lipoprotein cholesterol. Besides that, a number of studies have suggested PCSK9 may play a role in cancer biology. This is particularly true for gastroenteric (gastric and liver cancers) and lung cancers, where higher PCSK9 levels were associated with the increased ability of the tumor to develop and give metastasis as well as with reduced overall survival. Accordingly, monoclonal antibodies blocking PCSK9 were recently shown to synergize with immunotherapy in different types of cancers to achieve tumor growth suppression through an increased intratumoral infiltration of cytotoxic T cells. Anti-PCSK9 vaccines have been tested in animal models with encouraging results only in colon carcinoma. As most of this evidence is based on pre-clinical studies, this has led to some controversies and inconsistencies, thus suggesting that additional research is needed to clarify the topic. Finally, modulation of intracellular PCSK9 levels by silencing RNA (siRNA) may help understand the physiological and pathological mechanisms of PCSK9.

Association between Lipid Levels and Risk for Different Types of Aneurysms: A Mendelian Randomization Study

BACKGROUND

Although the associations between serum lipid levels and aneurysms have been investigated in epidemiological studies, causality remains unknown. Thus, this study aimed to investigate the causal relationships of serum high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), and triglyceride (TG) levels on five types of aneurysms, using genetic variants associated with four lipid traits as instrumental variables in a Mendelian randomization (MR) analysis.

METHODS

We performed two-sample Mendelian randomization (MR) analyses to evaluate the associations of HDL-C, LDL-C, TC, and TG levels with risks for five types of aneurysms and those of LDL-C- (HMGCR, NPC1L1, PCSK9, CETP, and LDLR) and TG-lowering targets (ANGPTL3 and LPL) with aneurysms.

RESULTS

The sample sizes of the included studies ranged from nearly 80,000 to 410,000. We found inverse associations between genetically predicted HDL-C levels and aortic (OR = 0.74, 95% CI = 0.65-0.85) and abdominal aortic aneurysms (0.58, 0.45-0.75). A 1-SD increase in LDL-C and TC levels was associated with increased risks for aortic (1.41, 1.26-1.58 and 1.36, 1.18-1.56, respectively) and abdominal aortic aneurysms (1.82, 1.48-2.22 and 1.55, 1.25-1.93, respectively). TG levels were significantly associated with aortic (1.36, 1.18-1.56) and lower extremity artery aneurysms (2.76, 1.48-5.14), but limited to cerebral aneurysm (1.23, 1.06-1.42). Secondary analyses revealed a relationship between genetically proxied LDL-C-lowering targets and all types of aneurysms; however, the drug targets remained heterogeneous. We found a weak association between TG-lowering therapies and aortic (ANGPTL3, 0.51, 0.29-0.89) and abdominal aortic aneurysms (LPL, 0.64, 0.44-0.94).

CONCLUSION

According to genetic evidence, lipid dysfunction is a causal risk factor for aneurysms. Lipid-lowering drugs may be a potential effective strategy in preventing and managing aneurysms.

Role of PCSK9 in Homocysteine-Accelerated Lipid Accumulation in Macrophages and Atherosclerosis in ApoE-/- Mice

Background: Homocysteine (Hcy) has been established as an independent risk factor for atherosclerosis, and the involvement of hyperhomocysteinemia (HHcy) in atherosclerotic lesions is complex. Proprotein convertase subtilisin kexin 9 (PCSK9) has vital importance in lipid metabolism, and its inhibitors have intense lipid-lowering and anti-atherosclerotic effects. However, the underlying effect of PCSK9 on HHcy-accelerated dyslipidemia of macrophages is still uncertain. The purpose of this study was to investigate the potential role of PCSK9 in Hcy-induced lipid accumulation and atherosclerotic lesions.

Methods:In vitro, gene and protein expressions were assessed by real-time quantitative PCR and western blot in THP-1 macrophages with Hcy incubation. Lipid accumulation and cholesterol efflux were evaluated with Hcy treatment. SBC-115076 was used to examine the role of PCSK9 in ATP-binding cassette transporter A1 and G1 (ABCA1 and ABCG1)-dependent cholesterol efflux. In vivo, lesion area, lipid deposition and collagen contents were determined in aortas of ApoE^−/− mice under a methionine diet. SBC-115076 was subcutaneously injected to explore the potential effects of PCSK9 inhibition on alleviating the severity of HHcy-related atherosclerotic lesions.

Results: In THP-1 macrophages, Hcy dose- and time-dependently promoted PCSK9 gene and protein levels without regulating the translation of Low-density lipoprotein receptor (LDLR). SBC-115076 used to inhibit PCSK9 largely alleviated lipid accumulation and reversed the cholesterol efflux to apolipoprotein-I(apoA-I) and high-density lipoprotein (HDL) mediated by ABCA1 and ABCG1. In ApoE^−/− mice, methionine diet induced HHcy caused larger lesion area and more lipid accumulation in aortic roots. SBC-115076 reduced atherosclerotic severity by reducing the lesion area and lipid accumulation and increasing expressions of ABCA1 and ABCG1 in macrophages from atherosclerotic plaque. In addition, SBC-115076 decreased plasma Hcy level and lipid profiles significantly.

Conclusion: PCSK9 promoted lipid accumulation via inhibiting cholesterol efflux mediated by ABCA1 and ABCG1 from macrophages and accelerated atherosclerotic lesions under HHcy treatment. Inhibiting PCSK9 may have anti-atherogenic properties in HHcy-accelerated atherosclerosis.

Increased serum PCSK9 in patients with idiopathic pulmonary arterial hypertension: insights from inflammatory cytokines

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an important and major player in the pathophysiology of hypercholesterolemia and atherosclerosis. Recently, PCSK9 has been implicated in the pathogenesis of inflammatory diseases. Whether PCSK9 is involved in idiopathic pulmonary arterial hypertension (IPAH) remains unclear. This study aimed to investigate the relationship between PCSK9 and IPAH. Serum PCSK9, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1 β (IL-1β), and monocyte chemotactic protein-1 (MCP-1) were measured by enzyme linked immunosorbent assay. Transthoracic echocardiography was performed among 40 IPAH patients and 20 control subjects. Hemodynamic data were collected via right heart catheterization in patients with IPAH. Serum PCSK9, TNF-α, IL-6, IL-1β, and MCP-1 levels were significantly higher in IPAH patients than in control subjects (p < 0.001). Among enrolled IPAH patients, PCSK9 levels were higher in WHO-FC III/IV patients compared with those in WHO-FC I/II (p < 0.05), and were positively correlated with TNF-α, IL-6, MCP-1, N-Terminal pro-brain natriuretic peptide, pulmonary arterial systolic pressure (r = 0.653, p < 0.001), pulmonary arterial diastolic pressure (r = 0.466, p = 0.002), mean pulmonary arterial pressure (mPAP, r = 0.730, <0.001), pulmonary vascular resistance (r = 0.488, p = 0.001), and right ventricle diameter (r = 0.563, p < 0.001). In multiple regression analysis, mPAP was strongly associated with serum PCSK9 (β = 0.694, p < 0.001), independent of other variables. Receiver operating characteristic curve analysis showed the optimal cutoff value of serum PCSK9 concentration for predicting IPAH was 90.67 ng/ml, with a sensitivity of 90.0% and a specificity of 85.0%. In conclusion, IPAH patients had elevated serum PCSK9 levels which correlated the presence and severity of pulmonary hypertension. PCSK9 may be a novel potential therapeutic target.

PCSK9: A Multi-Faceted Protein That Is Involved in Cardiovascular Biology

Pro-protein convertase subtilisin/kexin type 9 (PCSK9) is secreted mostly by hepatocytes and to a lesser extent by the intestine, pancreas, kidney, adipose tissue, and vascular cells. PCSK9 has been known to interact with the low-density lipoprotein receptor (LDLR) and chaperones the receptor to its degradation. In this manner, targeting PCSK9 is a novel attractive approach to reduce hyperlipidaemia and the risk for cardiovascular diseases. Recently, it has been recognised that the effects of PCSK9 in relation to cardiovascular complications are not only LDLR related, but that various LDLR-independent pathways and processes are also influenced. In this review, the various LDLR dependent and especially independent effects of PCSK9 on the cardiovascular system are discussed, followed by an overview of related PCSK9-polymorphisms and currently available and future therapeutic approaches to manipulate PCSK9 expression.

Reducing Cardiac Injury during ST-Elevation Myocardial Infarction: A Reasoned Approach to a Multitarget Therapeutic Strategy

The significant reduction in ‘ischemic time’ through capillary diffusion of primary percutaneous intervention (pPCI) has rendered myocardial-ischemia reperfusion injury (MIRI) prevention a major issue in order to improve the prognosis of ST elevation myocardial infarction (STEMI) patients. In fact, while the ischemic damage increases with the severity and the duration of blood flow reduction, reperfusion injury reaches its maximum with a moderate amount of ischemic injury. MIRI leads to the development of post-STEMI left ventricular remodeling (post-STEMI LVR), thereby increasing the risk of arrhythmias and heart failure. Single pharmacological and mechanical interventions have shown some benefits, but have not satisfactorily reduced mortality. Therefore, a multitarget therapeutic strategy is needed, but no univocal indications have come from the clinical trials performed so far. On the basis of the results of the consistent clinical studies analyzed in this review, we try to design a randomized clinical trial aimed at evaluating the effects of a reasoned multitarget therapeutic strategy on the prevention of post-STEMI LVR. In fact, we believe that the correct timing of pharmacological and mechanical intervention application, according to their specific ability to interfere with survival pathways, may significantly reduce the incidence of post-STEMI LVR and thus improve patient prognosis.

Variants of PCSK9 Gene Are Associated with Subclinical Atherosclerosis and Cardiometabolic Parameters in Mexicans. The GEA Project

Background: Coronary artery disease (CAD) is a chronic, inflammatory, and complex disease associated with vascular risk factors. Nowadays, the coronary artery calcium (CAC) is a specific marker of the presence and extent of atherosclerosis. Additionally, CAC is a predictor of future coronary events in asymptomatic individuals diagnosed with subclinical atherosclerosis (CAC > 0). In this study, our aim is to evaluate the participation of two polymorphisms of the PCSK9 gene as genetic markers for developing subclinical atherosclerosis and cardiometabolic risk factors in asymptomatic individuals. Methods: We analyzed two PCSK9 polymorphisms (rs2479409 and rs615563) in 394 individuals with subclinical atherosclerosis and 1102 healthy controls using real time- polymerase chain reaction (PCR). Results: Under various inheritance models adjusted for different confounding factors, the rs2479409 polymorphism was associated with an increased risk of developing subclinical atherosclerosis (OR = 1.53, P recessive = 0.041). Both polymorphisms were significantly associated with several cardiometabolic parameters. Conclusions: Our data suggest that rs2479409 polymorphism could be envisaged as a risk marker for subclinical atherosclerosis.

Therapies for the Treatment of Cardiovascular Disease Associated with Type 2 Diabetes and Dyslipidemia

Cardiovascular disease (CVD) is the leading cause of death worldwide and is the clinical manifestation of the atherosclerosis. Elevated LDL-cholesterol levels are the first line of therapy but the increasing prevalence in type 2 diabetes mellitus (T2DM) has positioned the cardiometabolic risk as the most relevant parameter for treatment. Therefore, the control of this risk, characterized by dyslipidemia, hypertension, obesity, and insulin resistance, has become a major goal in many experimental and clinical studies in the context of CVD. In the present review, we summarized experimental studies and clinical trials of recent anti-diabetic and lipid-lowering therapies targeted to reduce CVD. Specifically, incretin-based therapies, sodium-glucose co-transporter 2 inhibitors, and proprotein convertase subtilisin kexin 9 inactivating therapies are described. Moreover, the novel molecular mechanisms explaining the CVD protection of the drugs reviewed here indicate major effects on vascular cells, inflammatory cells, and cardiomyocytes, beyond their expected anti-diabetic and lipid-lowering control. The revealed key mechanism is a prevention of acute cardiovascular events by restraining atherosclerosis at early stages, with decreased leukocyte adhesion, recruitment, and foam cell formation, and increased plaque stability and diminished necrotic core in advanced plaques. These emergent cardiometabolic therapies have a promising future to reduce CVD burden.